Enhanced indication of network support of srvcc and/or voice-over-ims for an user equipment in an eps network

ABSTRACT

Embodiments of the present invention include a method for enhanced indication of network support of SRVCC and/or Voice-over-IMS for an User Equipment UE in an Evolved Packet System EPS network, said method comprising at least one step based on taking into account support of SRVCC and/or Voice-over-IMS by Radio Access Network RAN nodes and/or by Radio Access Technologies RATs available for SRVCC for said UE in said EPS network.

The present invention generally relates to mobile communication networksand systems.

Detailed descriptions of mobile communication networks and systems canbe found in the literature, in particular in Technical Specificationspublished by standardization bodies such as in particular 3GPP (3^(rd)Generation Partnership Project).

In such systems a mobile terminal (or User Equipment) has access, via anAccess Network, to a Core Network providing communication services.

An example of 3GPP system is 3G-LTE system, also called Evolved PacketSystem EPS, specified in particular in 3GPP TS 23.401. EPS includesEvolved Packet Core EPC providing IP connectivity services to an UserEquipment UE. EPC can be accessed by different Access Networks,including 3GPP Radio Access Networks (such as E-UTRAN or GERAN/UTRAN)and non-3GPP Access Networks.

In EPS, CS (Circuit-Switched) services (such as in particular voiceservices) can be delivered as IP-based services, via PS(Packet-Switched) domain EPC providing IP connectivity to an operator'sIMS network. Such functionality is also referred to as “Voice-over-IMS”(VoIMS), or “IMS voice over PS session”.

On the contrary, in systems such as 2G-GSM or 3G-UMTS, CS services (suchas for example voice services) can be delivered via CS(Circuit-Switched) domain.

Single Radio Voice Call Continuity SRVCC provides voice call continuitybetween IMS over Packet Switched PS access and Circuit Switched CSaccess for calls that are anchored in IMS when the User Equipment UE iscapable of transmitting/receiving on only one of those access networksat a given time. SRVCC functionality is specified in particular in 3GPPTS 23.216. SRVCC can be performed from E-UTRAN to different Radio AccessNetworks RANs or Radio Access Technologies RATs, such as in particular3GPP GERAN or UTRAN.

As specified in particular in 3GPP 23.216, an SRVCC-capable UE includesan SRVCC capability indication in an Attach Request message sent to aMobility Management Entity (MME) in EPC during an Attach or mobilitymanagement procedure, and the MME includes a “SRVCC operation possible”indication in a Initial Context Setup Request sent to the eNode B (inE-UTRAN), meaning that both UE and MME are SRVCC-capable. As specifiedin particular in 3GPP TS 23.401 and 24.301, the MME also informs the UEabout network support of IMS voice over PS session, with an IMS voiceover PS session indicator.

As recognized by the inventor, and as will be explained with more detaillater, there is a need to improve such indication of Voice-over-IMSand/or SRVCC network support. More generally, there is a need to improvevoice services support in EPS.

Embodiments of the present invention in particular addresses such needs.

These and other objects are achieved, in one aspect, by a method forenhanced indication of network/UE support of SRVCC and/or Voice-over-IMSfor an User Equipment UE in an Evolved Packet System EPS network.

In an embodiment, said method comprises at least one step based ontaking into account support of SRVCC and/or Voice-over-IMS by RadioAccess Network RAN nodes and/or by Radio Access Technologies RATsavailable for SRVCC for said UE in said EPS network.

These and other objects are achieved, in other aspects, by entities forperforming such method, said entities including, in particular E-UTRANentity (eNodeB), and EPC entity (Mobility Management Entity MME).

Some embodiments of apparatus and/or methods in accordance withembodiments of the present invention are now described, by way ofexample only, and with reference to the accompanying drawings, in which:

FIG. 1 is intended to illustrate in a simplified way an Attach orTracking Area Update procedure, enhanced according to a first embodimentof the present invention,

FIG. 2 is intended to illustrate in a simplified way an Attach orTracking Area Update procedure, enhanced according to a secondembodiment of the present invention.

As recalled above, currently the UE sends its global UTRAN/GERAN srvcccapability to the MME at NAS level. This capability is used by the MMEtogether with the EPC srvcc support in order to decide whether toindicate “VoIMS possible” or “VoIMS not supported” back to the UE overNAS in the Attach/TAU/RAU Accept message. This indication is alsoprovided to the eNB in the S1 Initial Context Request message within theSRVCC indication Information element so that whenever an SRVCC isnecessary the eNB knows whether MME and UE supports it.

In case the srvcc is from lte to umts, one problem comes if the targetRAN node doesn't support SRVCC. Indeed, the support of incoming srvcc byan RNC requires some specific function. Since the MME is not necessarilyaware of this target RNC capability but the source eNB is e.g. byconfiguration, the “VoIMS possible” or “VoIMS not supported” indicationcurrently sent to the UE over NAS may not take it into account. Thus theMME can perfectly indicate “VoIMS possible” to the UE, leading to VoIMScall being established while the target UTRAN doesn't support srvcc. Asa result, at time of handover the eNB cannot perform this srvcc whichlikely leads to release the call so that the UE can catch up 3 g again.Another problem is also when the UE has indicated its generalUTRAN/GERAN SRVCC capability to the MME but has not been tested for oneof the two (either GERAN or UTRAN). The source eNB would be aware of it(so called FGI bits received by eNB from UE) but not the MME again. Tosolve these two problems it is necessary to send some information fromsource eNB to MME before the MME does decide to send to the UE over theNAS the “VoIMS possible” or “VoIMS not supported” indication.

Embodiments of the present invention in particular enable to solve suchproblems and/or avoid such drawbacks.

Embodiments of the present invention in particular take advantage of thefact that the source LTE eNB is aware e.g. by configuration whether atarget RNC supports srvcc or not.

Embodiments of the present invention include providing the target RNCsrvcc capability from eNB to the MME (for the lte to umts srvcc case).

The sending of the capability from the eNB to the MME must be earlyenough so that the MME is made aware before making the decision “VoIMSpossible” or not to be sent to the UE. The target RNC srvcc capabilitycan be sent from eNB to MME over a UE-dedicated message such as the UECapability Info Indication message or the Initial Context Responsemessage or any new UE-dedicated uplink S1AP message.

Embodiments of the invention can be extended to the case where thetarget RNC capability is provided from eNB to MME in a non-UE dedicateduplink S1 message such S1 Setup Request or a new non-UE dedicated uplinkmessage.

Embodiments of the invention can be extended to cover other RATs i.e. toprovide any target RAT RAN srvcc capability from eNB to MME e.g. forGERAN, CDMA including capability concerning multiple RATs at the sametime.

Embodiments of the invention can also be extended to cover any AccessStratum (AS) information that the eNB has which would be needed/usefulby the MME in its decision to allow the UE for “VolMS possible” or not.For example, one such information may be related to the FGI bit i.e. theeNB is made aware by the UE whether the srvcc support towards a givenRAT has been implemented and tested or not.

Embodiments of the invention can also be extended to cover the sendingfrom the eNB to the MME of the support of “VoIMS capability” on thetarget RAN and RAT: this one would be useful in the context of a fullVoIMS deployment scenario because the MME could decide to allow the UEto start VoIMS calls knowing the wide support of VoIMS on all RATs andRAN nodes even though srvcc is not supported. The sending of this VoIMScapability support could also be per UE to cover cases such as the eNBchecks per UE if the frequency band where the target RAT supports VoIMSis a frequency band also supported by the UE. By further extension tocover any case where the operation of the VoIMS by the UE on the targetRAN/RAT node depends on some radio capabilities of the UE which areknown by the eNB.

In embodiments of the present invention providing a sending by the eNBto the MME of either “srvcc support” or “VoIMS support” on a targetRAT/RAN node which depends on a per UE radio capability of the involvedUE, two embodiments may be envisioned:

In a first embodiment, since the eNB receives the UE Radio Capabilitieswithin the Initial Context Setup Request message or later, the newindication from eNB to MME would be sent after that e.g. in InitialContext Setup Response or in a new message, and the AttachAccept/TAU/RAU Accept towards the UE would be sent only after that,embedded in an S1AP Downlink NAS Transport.

In a second embodiment, after receiving the Initial UE Message, the MMEcould trigger a new class 1 procedure where a new S1 downlink messagefirst sends the UE Radio capabilities to the eNB, then eNB responds withthe new indication from eNB to MME, then the MME sends theAttach/TAU/RAU Accept towards the UE within the S1AP Initial ContextSetup Request message.

The first embodiment is illustrated in a simplified way in FIG. 1. Inthe scenario in FIG. 1, the first embodiment is represented whereby theAttach/TAU/RAU Accept message would be sent after and separate ofInitial Context Setup Request.

The second embodiment is illustrated in a simplified way in FIG. 2. InFIG. 2 the second embodiment is represented allowing MME to send theAttach/TAU/RAU Accept message within the Initial Context Setup Request.

Embodiments of the invention allow the MME to make the right decisionwhether to authorize a UE to use VoIMS or not depending on the targetRAT or target RAN nodes capabilities (wrt “srvcc support” or “VoIMSsupport”) or even depending on some specific radio characteristicssupported by the UE and known by eNB (FGI bits, supported frequencybands, etc.).

On the contrary, in the prior art, the MME may decide to send “VoIMSpossible” to a UE in the Attach/TAU/RAU Accept message allowing the UEto start VoIMS calls which are likely to get dropped whenever handoverto target RAT/RAN node becomes necessary due to non support of “srvcc”or non support of “VoIMS” at this target RAT/RAN node.

In one aspect, there is provided a method for enhanced indication ofnetwork support of SRVCC and/or Voice-over-IMS for an User Equipment UEin an Evolved Packet System EPS network.

In an embodiment, said method comprises at least one step based ontaking into account support of SRVCC and/or Voice-over-IMS by RadioAccess Network RAN nodes and/or by Radio Access Technologies RATsavailable for SRVCC for said UE in said EPS network.

In an embodiment, said method comprises a step of:

-   -   an eNodeB serving said UE signalling to a Mobility Management        Entity MME serving said UE, information as to said        Voice-over-IMS and/or SRVCC support by Radio Access Network RAN        nodes and/or Radio Access Technologies RATs available for SRVCC        for said UE in said EPS network, referred to as Radio Access        Network RAN-level-support information.

In an embodiment, said method comprises a step of:

-   -   said eNodeB signalling said RAN-level-support information to        said MME during an Attach procedure or a mobility management        procedure for said UE.

In an embodiment, said method comprises a step of:

-   -   said eNodeB signalling said RAN-level support information to        said MME, in a message Initial Context Setup Response.

In an embodiment, said method comprises a step of:

-   -   said eNodeB signalling said RAN-level support information to        said MME, in a dedicated message.

In an embodiment, said method comprises a step of:

-   -   said eNodeB determining information as to said Voice-over-IMS        and/or SRVCC support by RAN nodes and/or Radio Access        Technologies RATs available for SRVCC for said UE in said EPS        network, referred to as Radio Access Network RAN-level-support        information.

In an embodiment, said method comprises a step of:

-   -   said eNodeB determining said RAN-level-support information,        using information as to radio capabilities of said UE, and/or        RAN configuration information.

In an embodiment, said method comprises a step of:

-   -   a Mobility Management MME serving said UE signalling said        information as to radio capabilities of said UE to said eNodeB.

In an embodiment, said method comprises a step of:

-   -   said MME signalling said information as to radio capabilities of        said UE to said eNodeB during an Attach procedure or a mobility        management procedure for said UE.

In an embodiment, said method comprises a step of:

-   -   said MME signalling said information as to radio capabilities of        said UE to said eNodeB in a message Initial Context Setup        Request.

In an embodiment, said method comprises a step of:

-   -   said MME signalling said information as to radio capabilities of        said UE to said eNodeB in a dedicated message.

In an embodiment, said method comprises a step of:

-   -   a Mobility Management Entity MME serving said UE sending a        Voice-over-IMS support indication to said UE, indicating        Voice-over-IMS supported, if Voice-over-IMS is supported by        Evolved Packet Core EPC, and if either Voice-over-IMS or SRVCC        is supported by at least one of said available RAN nodes and/or        RATs.

In an embodiment, said method comprises a step of:

-   -   a Mobility Management Entity MME serving said UE sending an        SRVCC support indication to an eNodeB serving said UE,        indicating SRVCC supported, if SRVCC is supported by Evolved        Packet Core EPC and by at least one of said available RAN nodes        and/or RATs.

Other aspects relate to entities comprising means for performing suchmethod, said entities including, in particular E-UTRAN entity (eNodeB),and EPC entity (Mobility Management Entity MME).

In one aspect, there is provided an eNode B serving an UE in an EPSnetwork, said eNodeB comprising:

-   -   means for signalling to a Mobility Management Entity MME serving        said UE, information as to Voice-over-IMS and/or SRVCC support        by RAN nodes and/or Radio Access Technologies RATs available for        SRVCC for said UE in said EPS network, referred to as Radio        Access Network RAN-level-support information.

In an embodiment, said eNode B comprises:

-   -   means for signalling said RAN-level-support information to a        Mobility Management MME serving said UE, during an Attach        procedure or a mobility management procedure for said UE.

In an embodiment, said eNode B comprises:

-   -   means for signalling said RAN-level support information to said        MME, in a message Initial Context Setup Response.

In an embodiment, said eNode B comprises:

-   -   means for signalling said RAN-level support information to said        MME, in a dedicated message.

In an embodiment, said eNode B comprises:

-   -   means for determining information as to said Voice-over-IMS        and/or

SRVCC support by RAN nodes and/or Radio Access Technologies RATsavailable for SRVCC for said UE in said EPS network, referred to asRadio Access Network RAN-level-support information.

In an embodiment, said eNode B comprises:

-   -   means for determining said RAN-level-support information, using        information as to radio capabilities of said UE, and/or RAN        configuration information.

In another aspect, there is provided a Mobility Management Entity MMEserving an UE in an EPS network, said MME comprising:

-   -   means for signalling information as to radio capabilities of        said UE to an eNodeB serving said UE.

In an embodiment, said MME comprises:

-   -   means for signalling said information as to radio capabilities        of said UE to said eNodeB during an Attach procedure or a        mobility management procedure for said UE.

In an embodiment, said MME comprises:

-   -   means for signalling said information as to radio capabilities        of said UE to said eNodeB in a message Initial Context Setup        Request.

In an embodiment, said MME comprises:

-   -   means for signalling said information as to radio capabilities        of said UE to said eNodeB in a dedicated message.

In another aspect, there is provided a Mobility Management Entity MMEserving an UE in an EPS network, said MME comprising:

-   -   means for sending a Voice-over-IMS support indication to said        UE, indicating Voice-over-IMS supported, if Voice-over-IMS is        supported by Evolved Packet Core EPC, and if either        Voice-over-IMS or SRVCC is supported by at least one of RAN        nodes and/or RATs available for SRVCC for said UE in said EPS        network.

In another aspect, there is provided a Mobility Management Entity MMEserving an UE in an EPS network, said MME comprising:

-   -   means for sending an SRVCC support indication to an eNodeB        serving said UE, indicating SRVCC supported, if SRVCC is        supported by Evolved Packet Core EPC and by at least one of said        available RAN nodes and/or RATs available for SRVCC for said UE        in said EPS network.

The detailed implementation of the above-mentioned means does not raiseany special problem for a person skilled in the art, and therefore suchmeans do not need to be more fully disclosed than has been made above,by their function, for a person skilled in the art.

A person of skill in the art would readily recognize that steps ofvarious above-described methods can be performed by programmedcomputers. Herein, some embodiments are also intended to cover programstorage devices, e.g., digital data storage media, which are machine orcomputer readable and encode machine-executable or computer-executableprograms of instructions, wherein said instructions perform some or allof the steps of said above-described methods. The program storagedevices may be, e.g., digital memories, magnetic storage media such as amagnetic disks and magnetic tapes, hard drives, or optically readabledigital data storage media. The embodiments are also intended to covercomputers programmed to perform said steps of the above-describedmethods.

1-15. (canceled)
 16. An apparatus comprising: at least one processor;and at least one memory including computer program code; the at leastone memory and the computer program code configured to, with the atleast one processor, cause the apparatus at least to: signal to a corenetwork entity serving an user equipment served by said apparatus in amobile communication network, information as to voice-over-IMS supportby radio access network nodes in said mobile communication network,wherein the information as to voice-over-IMS support by radio accessnetwork nodes comprises radio access network-level-support information,said signalling allowing a voice-over-IMS indication indicatingvoice-over-IMS supported or voice-over-IMS not supported sent by saidcore network entity to said user equipment to take said radio accessnetwork-level-support information into account.
 17. An apparatusaccording to claim 1, wherein the at least one memory and the computerprogram code are configured to, with the at least one processor, causethe apparatus to: signal said radio access network-level-supportinformation to said core network entity during one of an attachprocedure and a mobility management procedure for said user equipment.18. An apparatus according to claim 1, wherein the at least one memoryand the computer program code are configured to, with the at least oneprocessor, cause the apparatus to: signal said radio accessnetwork-level support information to said core network entity in adedicated message.
 19. An apparatus according to claim 1, wherein the atleast one memory and the computer program code are configured to, withthe at least one processor, cause the apparatus to: determine said radioaccess network-level support information.
 20. An apparatus according toclaim 1, wherein the at least one memory and the computer program codeare configured to, with the at least one processor, cause the apparatusto: determine said radio access network-level-support information usingat least one of information as to radio capabilities of said userequipment, and radio access network configuration information.
 21. Anapparatus according to claim 1, wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to: receive information as to radiocapabilities of said user equipment signalled to said apparatus by saidcore network entity.
 22. An apparatus according to claim 1, wherein theat least one memory and the computer program code are configured to,with the at least one processor, cause the apparatus to: receiveinformation as to radio capabilities of said user equipment signalled tosaid apparatus by said core network entity during at least one of anattach procedure and a mobility management procedure for said userequipment.
 23. An apparatus according to claim 1, wherein the at leastone memory and the computer program code are configured to, with the atleast one processor, cause the apparatus to: receive information as toradio capabilities of said user equipment signalled to said apparatus bysaid core network entity in a dedicated message.
 24. An apparatusaccording to claim 1, wherein the at least one memory and the computerprogram code are configured to, with the at least one processor, causethe apparatus to: during a procedure triggered by said core networkentity, first receive user equipment radio capabilities in a downlinksignaling message, and then respond with said radio accessnetwork-level-support information sent to said core network entity. 25.An apparatus, comprising: at least one processor; and at least onememory including computer program code; the at least one memory and thecomputer program code configured to, with the at least one processor,cause the apparatus at least to: receive from a radio access networknode serving a user equipment served by said apparatus in a mobilecommunication network, information as to voice-over-IMS support by radioaccess network nodes in said mobile communication network, wherein theinformation as to voice-over-IMS support by radio access network nodescomprises radio access network-level-support information, and send tosaid user equipment a voice-over-IMS support indication, indicatingvoice-over-IMS supported or voice-over-IMS not supported, taking intoaccount said radio access network-level support information.
 26. Anapparatus according to claim 10, wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to: receive said radio accessnetwork-level-support information during one of an attach procedure anda mobility management procedure for said user equipment.
 27. Anapparatus according to claim 10, wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to: receive said radio accessnetwork-level support information in a dedicated message.
 28. Anapparatus according to claim 10, wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to: signal information as to radiocapabilities of said user equipment to said serving radio access networknode.
 29. An apparatus according to claim 10, wherein the at least onememory and the computer program code are configured to, with the atleast one processor, cause the apparatus to: signal said information asto radio capabilities of said user equipment to said radio accessnetwork node during one of an attach procedure and a mobility managementprocedure for said user equipment.
 30. An apparatus according to claim10, wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus to:signal said information as to radio capabilities of said user equipmentto said serving radio access network node in a dedicated message.
 31. Anapparatus according to claim 10, wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to: trigger a procedure whereby userequipment radio capabilities are first sent to the serving radio accessnetwork node in a downlink signaling message, and then the apparatusreceives said radio access network-level-support information from saidserving radio access network node.
 32. An apparatus according to claim10, wherein the radio access network-level support information takesinto account information as to radio capabilities of said user equipmentand/or radio access network configuration information.
 33. A methodcomprising: signaling to a core network entity serving an user equipmentserved by a radio access network node in a mobile communication network,information as to voice-over-IMS support by radio access network nodesin said mobile communication network, wherein the information as tovoice-over-IMS support by radio access network nodes comprises radioaccess network-level-support information, said signalling allowing avoice-over-IMS indication indicating voice-over-IMS supported orvoice-over-IMS not supported sent by said core network entity to saiduser equipment to take said radio access network-level-supportinformation into account.
 34. A method comprising: receiving from aradio access network node serving a user equipment served by a corenetwork entity in a mobile communication network, information as tovoice-over-IMS support by radio access network nodes in said mobilecommunication network, wherein the information as to voice-over-IMSsupport by radio access network nodes comprises radio accessnetwork-level-support information, and sending to said user equipment avoice-over-IMS support indication, indicating voice-over-IMS supportedor voice-over-IMS not supported, taking into account said radio accessnetwork-level support information.